Hello List,

This is my first post on this mailing list. I have just begun working 
with Slony-I 1.1.5 with PostgreSQL 8.1.3 on RHEL4-AS.
I try to understand perfectly the mechanics of Slony-I and to do that, I 
replicate a database running on one server to a slave database running 
on an other server.

I read the documentation : http://linuxfinances.info/info/slony.html 
(very detailed, thanks !) but I didn't find a chapter or an other 
documentation in which all the "slon" processes created with the 
execution of the "slon_start" command are detailed.
I also tried to find a post of this mailing list, without success... I 
think this topic has been already discussed but I did not find an aswer.

Then I will describe you my test case : on the master node, I launched 
this command :
slon_start node1 2> /SLONY_PGS/log/slony_node1.err 1> 
/SLONY_PGS/log/slony_node1.out
and on the slave node, I launched this command :
slon_start node2 2> /SLONY_PGS/log/slony_node2.err 1> 
/SLONY_PGS/log/slony_node2.out
By doing this, I saw several slon process and I try to understand their 
"mission" and why they have been created.

On the master server, for which the IP address is 1.2.3.4 (not the real 
one ;-)), the command "ps -ef | grep post" gives me :
bash-3.00$ ps -ef | grep post
postgres  7168     1  0 13:58 pts/5    00:00:00 /usr/bin/postmaster
postgres  7181  7168  0 13:58 pts/5    00:00:00 postgres: logger 
process  postgres  7183  7168  0 13:58 pts/5    00:00:00 postgres: 
writer process  postgres  7184  7168  0 13:58 pts/5    00:00:00 
postgres: stats buffer process  postgres  7185  7184  0 13:58 pts/5    
00:00:00 postgres: stats collector process  postgres 29529     1  0 
14:53 pts/5    00:00:00 /usr/bin//slon -s 1000 -d2 replication 
host=1.2.3.4 dbname=cave user=slony port=5432
postgres 29538 29529  0 14:53 pts/5    00:00:01 /usr/bin//slon -s 1000 
-d2 replication host=1.2.3.4 dbname=cave user=slony port=5432
postgres 29541  7168  0 14:53 pts/5    00:00:01 postgres: slony cave 
1.2.3.4(45738) idle
postgres 29543     1  0 14:53 pts/5    00:00:00 /usr/bin/perl 
/usr/local/slony/bin/slon_watchdog 
--config=/usr/local/slony/etc/slon_tools.conf node1 30
postgres 29548  7168  0 14:53 pts/5    00:00:00 postgres: slony cave 
1.2.3.4(45739) idle
postgres 29549  7168  0 14:53 pts/5    00:00:01 postgres: slony cave 
1.2.3.4(45740) idle
postgres 29550  7168  0 14:53 pts/5    00:00:01 postgres: slony cave 
1.2.3.4(45742) idle
postgres   408  7168  0 14:55 pts/5    00:00:03 postgres: slony cave 
5.6.7.8(60773) idle

On the slave server, for which the IP address is 5.6.7.8 (not the real 
one too), I've got :
bash-3.00$ ps -ef | grep post
postgres 27670     1  0 13:58 pts/4    00:00:00 
/opt/postgre/V813/bin/postmaster
postgres 27698 27670  0 13:58 pts/4    00:00:00 postgres: writer 
process       postgres 27699 27670  0 13:58 pts/4    00:00:00 postgres: 
stats buffer process  postgres 27700 27699  0 13:58 pts/4    00:00:00 
postgres: stats collector process  postgres 14706 27670  0 14:53 
pts/4    00:00:03 postgres: slony cave 1.2.3.4(45741) idle
postgres 17843     1  0 14:55 pts/4    00:00:00 
/opt/postgre/V813/bin//slon -s 1000 -d2 replication host=5.6.7.8 
dbname=cave user=slony port=5432
postgres 17863 17843  0 14:55 pts/4    00:00:01 
/opt/postgre/V813/bin//slon -s 1000 -d2 replication host=5.6.7.8 
dbname=cave user=slony port=5432
postgres 17865     1  0 14:55 pts/4    00:00:00 /usr/bin/perl 
/usr/local/slony/bin/slon_watchdog 
--config=/usr/local/slony/etc/slon_tools.conf node2 30
postgres 17867 27670  0 14:55 pts/4    00:00:01 postgres: slony cave 
5.6.7.8(60769) idle
postgres 17881 27670  0 14:55 pts/4    00:00:00 postgres: slony cave 
5.6.7.8(60770) idle
postgres 17882 27670  0 14:55 pts/4    00:00:02 postgres: slony cave 
5.6.7.8(60771) idle
postgres 17884 27670  0 14:55 pts/4    00:00:01 postgres: slony cave 
5.6.7.8(60772) idle

Could you please explain me the goal of each slon processes on the 
master node, and on the slave node ?
Could you tell me how the number of slon processes has been created 
(decided) ?
Why do I have all these open connexions on the database ?

I hope someone could answer me or give me the links to the documentation 
in which I can find the answers.

Regards,
Alexandra DANTE